Various types of cooking vessels are known and used in a kitchen to cook food. Typical cooking apparatus such as a pan and a rice cooker are made of a single-layered stainless steel. The single-layered stainless steel is good for transferring heat fast, but has a disadvantage that food gets stuck to the cooking apparatus.
To solve the above problem, cooking vessels having a double-layered structure has been proposed.
Japanese Utility Model Laid-Open No. Sho56-169825 teaches a heating pot comprising an inner wall and an outer wall, wherein a closed space is provided therebetween, and a working fluid is injected, the working fluid vaporizing and moving by heating within the space, and condensing by cooling. Japanese Utility Model Laid-Open No. Sho63-48526 teaches a heat-insulated cooking apparatus, wherein a vacuum heat-insulated layer is formed in a container and in a side wall portion, and heat is transferred from a bottom portion, the container comprising the side wall portion and bottom portion.
However, such cooking vessels have the risk of explosion due to the pressure of substances between an inner wall and an outer wall.
Moreover, the typical cooking vessels have a problem that when cooking soup, soup within the vessels is leaked out so that vitamin is destroyed or escaping.